Actually I now realise that what I saw in Switzerland was not a circumzenithal arc, but instead a Sun Halo (at 22 degrees around the Sun).Oh I forgot, we also saw and photographed the circumzenithal arc around the sun which looks like an inverted rainbow in the sky. I've only seen it once before and that was in Scotland and my photo with a disposable film camera didn't do it justice.
I have indeed seen a true circumzenithal arc but that was at home in Scotland. It is different, it is not around the Sun, but instead around the zenith, above the Sun.